1. Field of the Invention
The present invention relates to a terminal for designing, programming, starting-up and/or maintaining an automatic control using a programmable controller.
2. Description of the Prior Art
It is generally known that a programmable controller usually comprises a given number of inputs for connection to the detection elements (sensors) of the process, a given number of control outputs for connection respectively to each of the actuators of the process and a processor for ensuring the sequential flow of the operations (control of the actuators) which the process must carry out, taking into account the data supplied by the detectors. For ensuring the timing of these operations, this processor uses a program specific to the process which it is desired to control. This program is generally generated in a computer or similar in an appropriate evolved language then, after processing by the computer (compliation), retranscribed into machine language so as to obtain an object program directly usable by the controller. This object program may then be transmitted to the controller directly by a connection provided for this purpose between the computer and the controller. It may also be stored in a peripheral memory such for example as a magnetic tape, a disk or even a memory programmable by the user (PROM), for example an erasable programmable memory (EPROM). In this case, the controller must necessarily be equipped with a corresponding read-out unit, for example a magnetic tape reader or a disk reader or even a connector for connecting the programmable memory.
Now, like all data processing systems, programming of the controller by conventional methods is carried out in two phases, namely:
a phase for analyzing the automatic control desired and which requires an analyst competent both in automatic working and in data processing and PA0 a programming phase properly speaking requiring purely data processing knowledge. PA0 a first phase during which there is formed if required on the screen, using the corresponding keys of the keyboard, a "contact" type representation of the safety arrangements and of the working modes of the process; PA0 a second phase during which a "sequential" type graphic representation is formed on the screen using the corresponding keys of the keyboard, defining the sequence of steps and transition conditions of the automatic control and, possibly, immediately after definition of each of the transitions, a contact type representation of the receptivities associated with this transition, and PA0 a third phase during which a "contact" type graphic representation is formed on the screen by means of the corresponding keys, defining the actions of the automatic control which must be carried out when the steps which are associated therewith are active. PA0 F: presence of one or more forced bits, PA0 !: presence of a fault in the terminal or the controller, this character being able to wink in the case of a new fault, PA0 A: this character lights up and possibly winks in the case of dangerous manipulation for certain manual operations. PA0 the list of the forced bits PA0 the list of the active bits PA0 a message indicating the dangerous manipulation.
It is clear that this duality of competences required for programming forms a considerable obstacle to the widespread use of programmable controllers. To try to overcome this disadvantage, terminals have already been produced comprising a keyboard, a screen and a processor for defining the automatic controls by means of diagrams formed on the screen in accordance with a graphic representation mode identifiable by the processor. In this case, the programming of the controller no longer requires an extensive data processing knowledge. The operator need only form the diagrams of the automatic control on the screen whereas the processor generates the program directly from these diagrams.
At the present time, a so-called "contact" graphic representation method is available for this which consists in representing the automatic control in the form of contacts and relay coils, as well as function blocks representing members such as counters, programmers, arithmetical operators etc. This graphic representation method is suitable for generating relatively simple automatic controls. On the other hand, it is not very practical in the case of more complex automatic controls, more especially because it does not show sufficiently clearly the sequential flow of the operations carried out by the process.
The aim of the invention is then to overcome this disadvantage. It therefore proposes a terminal which allows a controller to be programmed by using a graphic representation method which consists in the combination of the "contact" representation method and a so-called "sequential" representation method which springs from a method of analysis consisting in breaking down the operation of the machine or of the processs to be automated into a succession of steps and transitions, all chained together. With each step is associated a list of actions which are carried out when this step is active.